As an example, antenna systems used in two-way communications between two mobile carriers are usually provided with a pursuit function, the antenna of each of said carriers then having to cover a wide pointing surface area, so that the radio-electric axes of each antenna remain oriented facing one another, irrespective of the movements of the carriers. In order to orient the antenna in the desired directions, an antenna system comprises a positioner, that is to say a programmable controller comprising a mobile portion to which the antenna is attached.
A first category of positioners, called tower positioners, makes it possible to orient the antenna by making it pivot, on the one hand, about a vertical axis in order to modify the angle of relative bearing and, on the other hand, about a horizontal axis in order to modify the angle of elevation. The signals transmitted and/or received by the mobile antenna are transmitted to a fixed portion, for example to the mount of the positioner, via a waveguide. When the antenna system has a large range of movement in relative bearing, or even has infinite relative bearing—in other words, when it allows the antenna to pivot indefinitely about the vertical axis—, the use of rotating collectors and/or of rotating joints at the junction of the waveguide with the fixed portion is necessary in order to prevent subjecting the waveguide to torsional forces which would damage it. A drawback of such antenna systems is their high cost of production.
A second category of positioners, made on the principle of a Cardan suspension, makes it possible to dispense with collectors and rotating joints. Certain of these positioners benefit from an enhancement proposed in a patent application published under reference FR2769969 for the applicant “ACC ingénierie & maintenance SA”. These enhanced positioners comprise a pointing device with no top dead center based on a pantograph mechanism; they will be qualified in what follows as “pantograph positioners”. In order to convey the electromagnetic signals between the antenna and the fixed mount of a pantograph positioner, waveguides that are sufficiently flexible and accept the torsional movements are used.
These waveguides consist of a discontinuous structure, often on the basis of interlocked scales which lead to reliability problems. Specifically, the structure of such a waveguide wears very quickly, and even breaks under the effect of the repeated torsional movements that are applied to it. Thus, the service life of the waveguide is short, which imposes regular preventive replacements. Moreover, considerable insertion losses and intermodulation products appear when this type of waveguide is used. In transmission, the powers are then severely limited.